Despite the availability of potent analgesics and state-of-the-art guidelines for pain management, children continue to suffer from unrelieved pain. Developmental difficulties in pain assessment contribute to the persistence of this problem. Although numerous self-report tools exist, instruments that require the child s cooperation are problematic during acute illness. Clearly, the resolution of unnecessary pain in children requires alternate measures for pain assessment, measures independent of children's ability and willingness to help in the assessment. The purpose of this study is to: (a) evaluate the ability of selected physiologic variables (frontalis and forearm electromyogram, respiratory rate, heart rate, skin temperature, and galvanic skin conductance) to differentiate arousal of children and, (b) to explore relationships among physiologic variables and self-report measures of pain and emotional distress. A one group, repeated measures, randomized crossover design will guide the study. Chosen from a convenience sample, 100 healthy children (8-17 years) will serve as their own control while undergoing the cold pressor test and guided imagery to effect increased and decreased responses from baseline. Data analysis will include descriptive, univariate, and multivariate procedures. Addressing limitations of previous work, the proposed study will employ adequate power, a well controlled design, and equipment equal in sophistication to monitors used in clinical practice. Results promise to answer important questions about the utility of physiologic measures in assessing stress-induced arousal. Negative results would have profound implications for the wide spread clinical use of vital signs in judgments about children's pain.